Variation In Plant Leaf Vein Traits In Taibai Mountain And Their Relationships With Other Leaf Traits

Leaf functional traits are highly plastic and sensitive to environmental changes,and thus can reflect the plants’ adaptative mechanisms and influence the survival and growth of plants.Leaf vein,especially the minor vein,acts as the primary structure of water transport in leaves,which influences the water content and photosynthetic ability of leaves.In addition,plants usually modify several leaf functional traits together to adapt to environmental changes.Therefore,studying the leaf vein traits and their relationships with other leaf traits could help us understanding the plants’ adaptive strategies to external habitats,thereby providing theoretical basis for screening suitable species in different habitats.The minor vein traits,stomatal traits,specific leaf area,and leaf dry matter content of 194 common species were determined in the northern slope of Taibai Mountain.We examined the variation in minor vein traits along altitudinal gradients and their relationships with other leaf traits.Meanwhile,we compared the differences in leaf functional traits between the dominant and non-dominant species within communities.Our aim was to reveal the covariation mechanism of different leaf functional traits in response to environmental changes,and provide a theoretical framework for plant breeding and conservation,ecological restoration,and community assembly.Our results showed that:(1)Variation in minor vein traits along altitudinal gradients differed among plant growth forms.In trees,the minor vein diameter(VD)and vein volume(VV)increased gradually along the altitude(P<0.05),whereas the minor vein length per leaf area(VLA)did not change significantly along the altitude(P>0.05).There were no significant altitudinal trends of three minor vein traits in shrubs(P>0.05).In herbs,VLA and VV increased gradually along the altitude(P<0.05),while VD did not change significantly(P>0.05).Additionally,the correlations among vein traits varied among the different altitude and growth forms.Specifically,VLA and VV only displayed a positive correlation at 1370 m.Among different growth forms,VLA and VD showed a significantly positive correlation in trees and shrubs(P<0.01),while VLA and VV only showed a positive correlation in herbs(P<0.01).Environmental factors had a modest effect on minor vein traits when all species were considered.For different plant growth forms,climate and soil factors explained 25.0%–32.9%of variation in minor vein traits of trees,and 5.0%–15.0% in herbs,and only 13.1%explanation for VLA in shrubs.(2)There was a significant positive correlation between VLA and stomatal density(SD)(P<0.01),which remained significant after removing the effect of phylogeny by PIC(P<0.01).In addition,the positive relationship between VLA and SD existed at different altitudinal gradients,and this coordination gradually was enhanced with increasing altitude.Among different growth forms,there was a significant positive correlation between VLA and SD in shrubs and herbs(P<0.01),however,this relationship was decoupled in trees.Moreover,total minor vein length and total stomata numbers showed a strong positive correlation(P<0.001)in all species,trees,shrubs,and herbs.(3)In contrast to non-dominant species,dominant species owned higher average values of VLA,SD,SL,and leaf dry matter content(LDMC)(P<0.05),but lower specific leaf area(SLA)(P<0.05).VLA and VD showed trade-offs only in dominant species,while VLA and SD showed positive coordination only in non-dominant species(P<0.05).VLA related positively with SLA in dominant species,but negatively in non-dominant species.The negative relationship between VD and SLA occurred both in dominant and non-dominant species.Moreover,VLA and VD correlated positively with LDMC only in non-dominant species.In addition,there was a positive correlation between species’ relative dominance and SD in low altitude,but a negative correlation between species’ relative dominance and SLA in high altitude.In conclusion,leaf vein traits and their synergistic variation with other leaf traits are critical to plants’ ability to adapt to their environments and have an impact on species dominance.Therefore,in the silvicultural process,the dominance of species can be altered by utilizing the variations in leaf functional traits,encouraging the cohabitation of different tree species and boosting the community’s species diversity.